Manufacture of nitrosoguanidine



, Patented Feb. 7, 1939 I PATENT OFFICE MANUFACTURE. OF

NITRO SO GUANIDINE Edward B. W. Kerone, Alton, Ill., assignor to Western Cartridge Company, East Alton, 111., a corporation of Delaware No Drawing. Application June 30, 1934, Serial No. 733,325

18 Claims.

- are obtained.

In the reduction of nitroguanidine to form I nitrosoguanidine, as heretofore practiced or attempted, the -methods employed have been lengthy, difficult to carry out, uncontrollable and, therefore, uncertain so that such processes could not-be considered commercially practical. I-Ieretofore" such quantities of nitrosoguanidine as have been prepared have been prepared on a laboratory scale, and consequently little, if any, practical use has ever been made of nitrosoguanidine. The

reactions involved in the reduction of nitroguanidine to form nitrosoguanidine are exceedingly difilcult :to control since nitrosoguanidine is an intermediate compound between nitroguanidine 0 and aminoguanidine, which latter is the product offu-rther reduction beyond the nitrosoguanidine stage. '-Accordingly in the preparation of nitrosoguanidine, as heretofore practiced, the yield per .unit of nitroguanidine has'been extremely smalLand it has been difficult to separate the nitrosoguanidine from other products of the reaction and concomitant substances. Furthermore, it has heretofore been difiicult to prevent the nitrosoguanidine from breaking down into other compounds.

It isamong the objects of the present invention, generally stated, to provide an economical process for reducing organicnitraminesto nitrosamines.

A more specific object of the invention is to provide a process for reducing nitroguanidine to nitrosoguanidine.

Another object of this invention is to provide a'process of reducing organic compounds, partic- 40 ularly nitroguanidine, which is controllable to such an extent that the product will predominate in nitrosoguanidine. A more particular object ;of this invention is to provide a process of reducing nitroguanidine .45 wherein the quantity of reducing agent employed may be controlled and regulated in accordance with the product desired.

A furtherobject of this present invention is to provide a catalyst for a process of reducing nitro- 50 guanidine.

guanidine'maybe reduced to producecommercially practical yields of nitrosoguanidine. This may be accomplished by reducing the nitroguanidine as by means of a metallic reducing agent such as zinc in a slightly acid bath. The present invention contemplates that the quantity of the reducing agent employed maybe controlled and regulated so as to maintain conditions conducive to the production of nitrosoguanidine.

The present invention further contemplates that the reducing action should be carried out in a slightly, but positively, acid bath, since it is observed that the most satisfactory results are obtained from agents giving a high rate of reduction at low acidity. This may be accomplished by the use of a weak acid, for instance such as acetic acid, or it may be accomplished by the use of low concentrations of a strong acid, such for instance as hydrochloric or sulphuric acid. It is observed, however, that the reaction proceeds more rapidly with the weak acid than with the strong acid. In either case the action may be accelerated by the use of slightly acid salts, such as ammonium chloride, ammonium sulphate, calcium chloride, etc., and the yield will be found to be slightly greater when such accelerating agents or catalysts are employed.

Moreover, the present invention contemplates methods for reducing nitroguanidine to either aminoguanidine or nitrosoguanidine wherein the reduction of nitroguanidine is controlled by the relative amount of reducing agent employed. When zinc is used as the reducing agent the amount of acid and/or catalyst employed in the process may be varied considerably without significant effect upon the reduction. This shows that it is the reducing couple zinc-acid which determines the extent of the reduction, and indicates that the process may be controlled through controlling the zinc. In the preparation of nitrosoguanidine, employing the zinc-acid reducingcouple the reaction proceeds according to the following equation:

where A is any acid radical.

In practice the optimum amount of zinc for each gram molecular Weight of nitroguanidine (104 grams) is about '72 grams. Advantageous results can, however, be obtained with the use of from 65.4 to 81.8 grams of zinc per 104 grams of nitroguanidine. It will be observed that this proportion of reducing agent to nitroguanidine is rather close to the amount demanded by theory,

and since in the production of nitrosoguanidine it is necessary to remove one oxygen from the nitroguanidine, it will be observed that the amount of Zinc employed exceeds the equivalent Weight of oxygen. to be removed. by 0-25 percent.

In the production of aminoguanidine, however, it is observed that the optimum amount of the zinc is about 196.2 grams per molecular weight of nitroguanidine. obtained from the use of 196.2-294 grams of the zinc per 104 grams of nitroguanidine. In this case it will be observed that the amount of zinc required closely corresponds to the amount required by theory for displacing the two oxygens and adding hydrogen required to produce aminoguanidine, that is, removing two oxygens from the nitroguanidine and supplying extra hydrogens from some source, such for instance as water.

In carrying out the reduction to produce nitrosoguanidine, the nitroguanidine may be carried in a suitable amount of water to which may be added suitable amounts of an acid, such for in.- stance, as acetic, hydrochloric or sulphuric. There may also be added to this bath suitable quantities of catalysts, or accelerating agents among which neutral or slightly acid salts, such as ammonium chloride, ammonium sulphate, calcium chloride, etc., have been found to produce beneficial effects. Acetic acid, as a general rule, reacts with suificient rapidity to be employed alone, although a noticeable acceleration takes place upon the addition of a catalyzer, such as ammonium chloride. With hydrochloride acid and sulphuric acid their action usually proceeds slowly unless ammonium chloride or some other catalyzer is present in which case their action proceeds with satisfactory speed.

In general the nitroguanidine may be made up in the form of a slurry using any suitable amount of water and to this bath may be added the desired amount of zinc dust, the acid and the catalyzer, if the latter is employed. During the addition of the various substances to the nitroguanidine slurry itshould be vigorously agitated. Care should be taken particularly in producing nitrosoguanidine to maintain the temperature of the bath sufficiently low that decomposition of the nitrosoguanidine will not take place. This may be accomplished by suitably water-jacketing or icing the vessel in which the nitroguanidine is being treated and, as a general rule, the temperature should be maintained at or below 30 C. during the reaction.

The agitation may continue until the metallic Zinc entirely disappears, which time may be determined by drawing periodic samples and observing the presence or absence of metallic zinc. As a general rule, after the agitation has continued for one hour to one hour and fifteen minutes the metallic-zinc will have completely disappeared indicating that the reaction is complete and the mixture may then be cooled to about 10 C. The yellow solid, nitrosoguanidine, may be filtered off and washed until free of acid and dried at about C. H

The product obtained from the'process of the present invention may contain a very small amount of impurity (probably nitroguanidine) which apparently has no deleterious effect upon the nitrosoguanidine. If, however, a pure product is desired, this may be obtained by forming the copper salt of nitrosoguanidine which may be easily separated. The nitrosoguani'dine may be regenerated with an aqueous solution of an alkali cyanide, or any substance which forms a Advantageous results may be complex copper ion, but which does not injure the nitrosoguanidine. This method is particularly suitable for reclaiming the nitrosoguanidine the disclosure-of the process, it is suggested that the action may be as follows: The zinc actually withdraws the oxygen from the nitroguanidine and forms a zinc oxide coating upon the particles of zinc powder, while the acid or acid-catalyst combination concurrently attacks the oxide decoating the particles so that the activity of the zinc powder is maintained.

When a slightly acid salt, such as ammonium chloride, is employed it is observed that themost satisfactory results are obtained when an acid, such as hydrochloric acid, is added with just sufiicient rapidity that there is no odor of free ammonia. The addition of the acid at thisrate prevents the system from becoming alkaline and.

prevents the zinc from breaking down the ammonium chloride in accordance with the following equation:

This might be followed by the reaction:

2NH3+2H O+ZnOl 2NH o1+zn oH g In other words, the

chloride were used alone, but the addition of an acid prevents the reactions above, so that the reaction proceeds with good rapidity, the zinc being directly oxidized by the nitroguanidine, and this followed by the solution of the oxide film in the acid-catalyst combination, as suggested above.

To illustrate more in detail specific procedures which may be followed in practicing the present invention, advantageous results may be obtained by use of the respective products in the following proportions:

Nitroguanidine (finely divided) g 4000 Zinc dust (at least thru 325 mesh A screen) g 2500-3150 Glacial acetic acid 99.5% g 6000-7500 Water (amount not critical) 1iters 95 Ice (amount not critical) 1bs r 25 added'and this may be followed by the gradual,

addition of the acetic acid,,asfor instanceiin' 500 cc. portions. idly as the temperature may permit, it being The acid, may be added as rap- 7 I advisable to stay below 30 C. -As pointed out above, the vessel may be suitably cooled, as for instance by a water-jacket or icing. After all the acid has been added portions'oi the mixture may be .drawn'and observed, and when no metallic zinc remains which is usually'from one hour toone hour and ten'minutes, the mixture may be cooled to about 10 C. with about twenty-five pounds of ice. The yellow solid, nitrosoguanidine, may be filtered off, as above described, the yield being as high as 82% of the theory.

As a modified procedure from 1250-9200 grams of ammonium chloride may be added immediately after the zinc dust. The acetic acid is added at just such a rate that the solution remains at all times slightly, but distinctly, acid. The yield is a trifle higher than in the first procedure.

As a further embodiment the procedure first described may be followed, except that from 1250-9200 grams of ammonium'chloride is added just prior to the addition of the zinc dust, and instead of using acetic acid, 6900-8'700 cc. of 12 normal hydrochloric acid may be employed. The

ield is somewhat lower.

From the foregoing description it is apparent that the invention accomplishes its objects and that a process is provided whereby organic nitro compounds may be reduced and the reduction so controlled that the desired products are obin their descriptive and not in their limiting senses, and it is to be understood that the present invention contemplates the use of substances equivalent to the specific substances herein mentioned. It is to be particularly understood, therefore, that the invention is not limited to the specific details which have been set forth hereinbefore, but that such modifications and the use of such individual features and sub-combinations of features, as do not departfrom the spirit of this invention are, although not specifically described herein, contemplated by and within the scope of the appended claims.

Having thus described the invention, what is claimed is:

1. In the art of reducing nitroguanidine to nitrosoguanidine, the process comprising treating the nitroguanidine in an aqueous bath with subdivided reducing metal in proportions exceeding by 0-25% of the equivalent weight of oxygen to be displaced.

2. In the art of reducing nitroguanidine to nitrosoguanidine, the process comprising treating the nitroguanidine in a weakly acid aqueous bath with sub-divided reducing metal in proportions. exceeding by 0-25% of the equivalent Weight of oxygento be displaced.

3. In the art of reducing nitroguanidine to nitrosoguanidine, the process comprising treating,

nitroguanidine in an acidified aqueous bath with a quantity of zinc exceeding by '025% of the amount sufiicient to supply the electrons required for the desired reduction.

, 4. In the art of making nitrosoguanidine, the

process comprising, treating nitroguanidine in an aqueous bath containing 65.4-81.8 grams of zinc per molecular weight of nitroguanidine.

, 5. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in an aqueous bath with powdered zinc weighing 62.5-79% of the weight of nitroguanidine, and gradually adding acetic acid.

6. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in an aqueous bath with powdered zinc weighing 62.5-'79% of the weight of the nitroguanidine, and gradually adding acetic acid while the temperature of the bath is maintained below 30 C.

7. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in an aqueous bath with powdered zinc weighing 62.5-79% of the weight of nitroguanidine, and gradually adding acetic acid amounting to 1.5-1.8? times the weight of the nitroguanidine.

8. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in a bath with powdered zinc, acid, and a neutral or slightly acid salt of a class consisting of ammonium chloride, ammonium sulphate and calcium chloride until the metallic zinc disappears.

9. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in a bath with powdered zinc, an acid, and a neutral or slightly acid salt with which zinc will react while the temperature is maintained below 30 C. until the metallic zinc disappears.

10. In the art of making nitrosoguanidine, the process comprising, treating nitroguanidine in a water bath with a quantity of zinc exceeding by 0-25% the amount sufficient to supply the electrons required for the reduction desired, and concurrently dissolving the zinc reaction product.

11. In the art of making nitrosoguanidine, the process comprising, treating nitroguanidine in a bath containing powdered zinc, acetic acid, and ammonium chloride.

12. In the art of making nitrosoguanidine, the process comprising, treating nitroguanidine in a bath containing powdered zinc, hydrochloric acid, and ammonium chloride.

13. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in an aqueous bath containing: zinc powder 62.5- 79% of the weight of the nitroguanidine, and ammonium chloride 30-230% of the weight of the nitroguanidine.

14. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in a bath containing: zinc powder 62.5-79% of the weight of the nitroguanidine, and ammonium chloride 30-230% of the weight of the nitroguanidine; and adding acid during the agitation until the metallic zinc disappears.

15. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in a bath containing: zinc powder 62.5-79% of the weight of the nitroguanidine, and ammonium chloride 30230% of the weight of the nitroguanidine; and adding acid at a rate sufiicient to prevent liberation of free ammonia.

16. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in a bath containing: zinc powder 62.5-79% of the weight of the nitroguanidine, and ammonium chloride 30-230% of the weight of the nitroguanidine, and gradually adding acetic acid 1.5-1.8? times the weight of the nitroguanidine.

17. In the art of making nitrosoguanidine, the process comprising, agitating nitroguanidine in a water bath containing powdered zinc in an amount exceeding by 0-25% of the equivalent of oxygen to be displaced from the nitroguanidine, said bath containing a zinc oxide and zinc hydroxide solubilizing compound of the class consisting of acids and acid salts which when disi solved in water are acidic.

EDWARD B. W. KERONE. 

